Add a whenError() callback to retry requests that error (#3)
See dart-lang/pub#1826
diff --git a/CHANGELOG.md b/CHANGELOG.md
index ced9768..d1aa163 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,8 @@
+## 0.1.1
+
+* Add a `whenError()` parameter to allow requests to be retried when they
+ encounter networking errors.
+
## 0.1.0
* Initial version.
diff --git a/lib/http_retry.dart b/lib/http_retry.dart
index 4f30e03..e1b08fd 100644
--- a/lib/http_retry.dart
+++ b/lib/http_retry.dart
@@ -19,6 +19,9 @@
/// The callback that determines whether a request should be retried.
final bool Function(BaseResponse) _when;
+ /// The callback that determines whether a request when an error is thrown.
+ final bool Function(dynamic, StackTrace) _whenError;
+
/// The callback that determines how long to wait before retrying a request.
final Duration Function(int) _delay;
@@ -32,7 +35,8 @@
///
/// By default, this retries requests whose responses have status code 503
/// Temporary Failure. If [when] is passed, it retries any request for whose
- /// response [when] returns `true`.
+ /// response [when] returns `true`. If [whenError] is passed, it also retries
+ /// any request that throws an error for which [whenError] returns `true`.
///
/// By default, this waits 500ms between the original request and the first
/// retry, then increases the delay by 1.5x for each subsequent retry. If
@@ -40,14 +44,18 @@
/// given (zero-based) retry.
///
/// If [onRetry] is passed, it's called immediately before each retry so that
- /// the client has a chance to perform side effects like logging.
+ /// the client has a chance to perform side effects like logging. The
+ /// `response` parameter will be null if the request was retried due to an
+ /// error for which [whenError] returned `true`.
RetryClient(this._inner,
{int retries,
bool when(BaseResponse response),
+ bool whenError(error, StackTrace stackTrace),
Duration delay(int retryCount),
void onRetry(BaseRequest request, BaseResponse response, int retryCount)})
: _retries = retries ?? 3,
_when = when ?? ((response) => response.statusCode == 503),
+ _whenError = whenError ?? ((_, __) => false),
_delay = delay ??
((retryCount) =>
new Duration(milliseconds: 500) * math.pow(1.5, retryCount)),
@@ -63,16 +71,20 @@
/// `delays[1]` after the first retry, and so on.
RetryClient.withDelays(Client inner, Iterable<Duration> delays,
{bool when(BaseResponse response),
+ bool whenError(error, StackTrace stackTrace),
void onRetry(BaseRequest request, BaseResponse response, int retryCount)})
- : this._withDelays(inner, delays.toList(), when: when, onRetry: onRetry);
+ : this._withDelays(inner, delays.toList(),
+ when: when, whenError: whenError, onRetry: onRetry);
RetryClient._withDelays(Client inner, List<Duration> delays,
{bool when(BaseResponse response),
+ bool whenError(error, StackTrace stackTrace),
void onRetry(BaseRequest request, BaseResponse response, int retryCount)})
: this(inner,
retries: delays.length,
delay: (retryCount) => delays[retryCount],
when: when,
+ whenError: whenError,
onRetry: onRetry);
Future<StreamedResponse> send(BaseRequest request) async {
@@ -80,12 +92,21 @@
var i = 0;
while (true) {
- var response = await _inner.send(_copyRequest(request, splitter.split()));
- if (i == _retries || !_when(response)) return response;
+ StreamedResponse response;
+ try {
+ response = await _inner.send(_copyRequest(request, splitter.split()));
+ } catch (error, stackTrace) {
+ if (i == _retries || !_whenError(error, stackTrace)) rethrow;
+ }
- // Make sure the response stream is listened to so that we don't leave
- // dangling connections.
- response.stream.listen((_) {}).cancel()?.catchError((_) {});
+ if (response != null) {
+ if (i == _retries || !_when(response)) return response;
+
+ // Make sure the response stream is listened to so that we don't leave
+ // dangling connections.
+ response.stream.listen((_) {}).cancel()?.catchError((_) {});
+ }
+
await new Future.delayed(_delay(i));
if (_onRetry != null) _onRetry(request, response, i);
i++;
diff --git a/pubspec.yaml b/pubspec.yaml
index b2b3c7e..030ad20 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
name: http_retry
-version: 0.1.0
+version: 0.1.1
description: HTTP client middleware that automatically retries requests.
author: Dart Team <misc@dartlang.org>
homepage: https://github.com/dart-lang/http_retry
diff --git a/test/http_retry_test.dart b/test/http_retry_test.dart
index a0f4d30..29ab172 100644
--- a/test/http_retry_test.dart
+++ b/test/http_retry_test.dart
@@ -66,6 +66,31 @@
expect(response.statusCode, equals(503));
});
+ test("retries on any request where whenError() returns true", () async {
+ var count = 0;
+ var client = new RetryClient(
+ new MockClient(expectAsync1((request) async {
+ count++;
+ if (count < 2) throw "oh no";
+ return new Response("", 200);
+ }, count: 2)),
+ whenError: (error, _) => error == "oh no",
+ delay: (_) => Duration.ZERO);
+
+ var response = await client.get("http://example.org");
+ expect(response.statusCode, equals(200));
+ });
+
+ test("doesn't retry a request where whenError() returns false", () async {
+ var count = 0;
+ var client = new RetryClient(
+ new MockClient(expectAsync1((request) async => throw "oh no")),
+ whenError: (error, _) => error == "oh yeah",
+ delay: (_) => Duration.ZERO);
+
+ expect(client.get("http://example.org"), throwsA("oh no"));
+ });
+
test("retries three times by default", () async {
var client = new RetryClient(
new MockClient(
